Female lamprey fish mate hundreds of times but save their eggs

Female lamprey fish lead bold and exciting lives, but don’t assume that means they’re reckless about selecting a mate. According to new research from scientists at Hokkaido University in Japan, a single female lamprey fish will mate with as many as 10 males up to 100 times each. However, despite the high number of sexual interactions, the female lamprey fish will only release their eggs a limited number of times.

Lampreys are notoriously promiscuous, but scientists remain unsure of why the species prefers this method of reproduction. After all, it does require a much higher energy expenditure and increases the risk of predatory attack.

Of course, the male lamprey fish still release their sperm regardless of whether or not the females have laid an egg. Scientists have hypothesized that this style of “sham mating” allows the females to “test out” and evaluate the males before selecting a mate.

In order to test the hypothesis, the team of researchers conducted an experiment by setting up two experimental areas. Experiment Area A had one male and one female, while Experiment Area B had three males and one female. The results showed that “sham mating” increased as the number of males increased, while the number of eggs released decreased.

“The discovery of pre-breeding mate selection in highly promiscuous creatures is a new finding and of great interest,” said Dr. Chitose Koizumi, who led the study. “The study shows there is a possibility that, despite the presence of many males, females recognize individual males and actively control when they release their eggs.”

“This depends on the body size, nest-building abilities, and other qualities of the male. It is highly advantageous for females if they can choose their mate even when a large number of females and males gather at a single spawning site. Even though our results are only preliminary, further examination of the lampreys’ breeding behavior should give us a deeper understanding of mate selection and the evolution of breeding systems.”